Microdots and other taggants or identification devices are commonly attached to or incorporated within items of value in order to identify ownership or origin and to hinder theft, diversion, or illegal use of such items. Typical examples of such items include, but are not limited to, motor vehicles, motorcycles, machinery, equipment, branded products, spirits, high-value consumer goods, documents, storage media, and financial and other instruments.
For at least the last sixty years, exceedingly small photographic reproductions have been employed to confidentially communicate sensitive information. In such techniques, letter-sized documents have, for example, been copied onto a “microdot” no larger than a typewritten period. Such microdots may be physically hidden as periods in written or typewritten communications. The data borne by the microdot may be read by observing the microdot using a suitable microscope or other optical magnification means. Such microdots are typically circular with a diameter of approximately 1 millimeter and a thickness of a fraction of a millimeter.
Microdots of the type referred to above typically have flat surfaces bearing repetitive identifying indicia, such as numeric and alpha-numeric characters, which can be visually interpreted or retrieved under magnification. The indicia, whose smallest features (e.g., the middle stroke on a capital “E” character) are typically 2-5 micrometers in size, may provide part or all of a code that uniquely identifies the object to which a microdot is attached. On account of being exceedingly small, such microdots are generally not readily apparent to the naked human eye when attached to an item of value. Multiple microdots may be attached at different locations on the item, thus making complete removal of the microdots effectively impossible and thereby hindering attempts to hide the ownership or origin of the item.
Traditional methods of manufacturing metallic microdots employed combinations of holographic, photoresist, electroplating and metal-etching techniques. Traditional metallic microdots:                are exceedingly laborious and expensive to produce with significant amounts of the production being done literally by hand (thereby leading to high cost);        in the case of holographic dots, require the use of an e-beam machine and several weeks lead-time in order to produce a holographic master;        in the case of non-holographic dots, require one to two weeks in order to commission the variable data master;        can only be created from metal elements that are capable of being deposited by electroplating methods and/or etched by acid and are thus almost exclusively made of nickel; and        require the use of galvanic baths and or acid processes.        
A need therefore exists for alternative and new methods that are more suitable for mass production of microdots.